Democratic National Committee chairman Tom Perez became the first head of the party to demand ideological purity on abortion rights, promising Friday to support only Democratic candidates who back a woman’s right to choose.

“Every Democrat, like every American, should support a woman’s right to make her own choices about her body and her health,” Perez said in a statement. “That is not negotiable and should not change city by city or state by state.”

“At a time when women’s rights are under assault from the White House, the Republican Congress, and in states across the country,” he added, “we must speak up for this principle as loudly as ever and with one voice.”